(1) Turn off power to the upconverter and turn
Calculate and record the LNA gain by
on power to the LNA. Allow one hour for warmup.
taking the algebraic difference between the levels of step
Loosen the captive screws fasteners on
18 above and LNA output levels of steps 14 thru 17
the front panel of an upconverter drawer and pull the
drawer forward on its slides.
The gain should be within the limits of 39
2.0 dB at each measured frequency. If such is the
Disconnect cable W-5 going from the
synthesizer of the upconverter at J2 on module A4 and
case, proceed to the downconverter gain calibration step
connect the same to the hard limiter test assembly (SM-
3-14b. If not, proceed to step 21 below.
A-934943) through test cable assembly SM- C-935488-1
Plot the power output reading vs.
and the SMA adapter provided.
frequency on a graph. It is desirable to have a flat or
Loosen the captive screws on the front
slightly positive slope of the LNA gain characteristic (fig.
panel of the LNA control/translator drawer and pull the
drawer forward on its slides.
The LNA gain/slope may be adjusted by
Disconnect connector A2P53 going to
removing the access covers and weatherproofing plugs
receptacle J8 (SHF OUT) at the rear of the LNA
control/translator drawer, and connect it to the output of
special thin wall socket nut driver is required to loosen
the limiter SM-A-934943.
the lock nut on the screwdriver adjustment for the LNA
At the AME assembly, disconnect the
pump power and bias controls which affect the
terminal loop test cable (30A1W10) from the loop test
gain/slope of the LNA. A CW rotation of the adjustment
coupler input and connect the cable to the RF power
screw produces a negative slope and vice versa; the
meter with low power head (HP-8484A) using a UG-
adjustment sensitivity is approximately 5 dB/quarter turn.
The bias control mainly affects the low frequency gain;
Configure the shelter for normal
however, both controls interact and therefore may
operation and turn the power ON except that the power
require alternate repeated adjustments.
Tune the upconverter synthesizer test
Access to LNA No. 1 adjustment may
signal source to 8399.000 MHz and measure and record
be improved by temporary removal of
the signal level.
the W/G switch cable.
Repeat step 8 above at 8300.00Mhz.
(23) If the gain of the LNA at the four frequencies
Repeat step 8 above at 8200.00 MHz.
is not within 2 dB of 39 dB, adjust the bias control until
Repeat step 8 above at 7950.00 MHz.
such is achieved. It also may be necessary to adjust the
Disconnect the loop test cable from the
pump control slightly. To expedite the adjustment
RF power meter and connect the cable to the waveguide
procedure, calculate and record the output level range
switch test input through the 14 dB and 6dB series
limits in dBm for each frequency by adding 37 and 41 dB
attenuators provided (Sm-A-937237-1, and -3).
to the input levels calculated in step 18. For example an
Disconnect the output cable from the
input level of - 64 dBm will have an LNA output range of -
LNA to be tested and connect the HP436A Power Meter
27 to - 23 dBm.
with HP 8484A power head (using a UG-298/U adapter)
The adjustment should be performed in
to the LNA-1 or LNA-2 output port as the case may be,
accordance with conditions and procedures shown in
as selected at the LNA control/translator.
With the test signal applied to the
It may be necessary to perform the
LNA test port of the W/G switch, LNA
adjustment procedures several times
#2 is being tested with selector
to obtain the correct limits. It is
switch to the LNA #1 on the LNA
better to make several slight
adjustments to the controls instead
Tune the synthesizer in the upconverter
of attempting one large adjustment.
drawer to 7950.00 MHz. Read and record the output
(25) After the gain is correctly adjusted, lock the
level on the HP436A Power Meter.
controls in accordance with the following:
Repeat step 14 above at 8200.000 MHz.
(a) Set the synthesizer at 8399 MHz and
Repeat step 14 above at 8300.000 MHz.
note the reading on the power meter. This reading must
Repeat step 14 above at 8399.000 MHz.
be maintained when locking the controls.
Calculate and record the LNA input level
for each frequency by decreasing the measured levels of
steps 8 through 11 above by 20 dB.